1. Field of the Invention
This invention relates to an image blur correction apparatus for correcting image blur caused by a shake, vibrations or the like of an image pickup apparatus upon image pickup by such control as to move, upon occurrence of such a shake or the like of the image pickup apparatus, a correction lens in a direction perpendicular to an optical axis of a lens system so that the optical axis of the correction lens may be brought into alignment with the optical axis of the lens system. The present invention further relates to a lens apparatus having an image blur correction apparatus of the type described and an image pickup apparatus which includes a lens apparatus of the type described.
2. Description of the Related Art
In recent years, image pickup apparatus such as digital still cameras and video cameras have exhibited remarkable enhancement in performance, and now, everybody can simply pick up a still picture or a moving picture of high picture quality and high performance. Such enhancement in performance of image pickup apparatus relies much upon improvement in performance of a lens, a CCD element (solid-state image pickup element) and an image processing circuit.
However, in whatever manner the performance of a lens, a CCD element and so forth is improved, if a shake or a sway occurs with a hand which supports the camera (image pickup apparatus), then a shake occurs with a screen especially having a high resolution, resulting in blur of a picked up image. Therefore, some comparatively high-priced cameras incorporate an image blur correction apparatus for correcting image blur which arises from a shake or the like of the image pickup apparatus upon image pickup. However, such image blur correction as described is demanded originally not by such a high class model as is used by a professional who professionally picks up an image but by the majority of the public who have rather poor image pickup experience. In other words, the image blur correction is demanded by image pickup apparatus of popular models.
Further, strong demands for reduction in size and weight are directed to cameras (image pickup apparatus), and generally cameras which are light in weight and easy to handle are used favorably. However, existing image blur correction apparatus have a comparatively great size. Therefore, if an existing image blur correction apparatus is incorporated in a camera body, then the camera comes to have a correspondingly increased size, contrary to the demand for reduction in size and weight. Besides, existing image blur correction apparatus require a large number of parts and have a problem that a high cost is demanded by the increased number of parts.
A lens apparatus of the type described is disclosed, for example, in Japanese Patent Laid-Open No. Hei 3-186823 (hereinafter referred to as Patent Document 1). In particular, Patent Document 1 discloses a lens apparatus which incorporates an anti-vibration apparatus disposed in a camera or the like for detecting vibrations of a comparatively low frequency and preventing image blur using the detected vibrations as information for image blur prevention. The anti-vibration apparatus disclosed in Patent Document 1 is hereinafter referred to as first background art apparatus. The first background art apparatus is a camera anti-prevention apparatus including a correction optical mechanism disposed in a lens barrel having lens groups held thereon and configured to displace the optical axis of the lens groups, a vibration detection section configured to detect vibrations applied to the lens barrel, and an anti-vibration control section configured to drive the correction optical mechanism based on a signal from the vibration detection section to perform anti-prevention action. The correction optical system includes a correction lens, a fixing frame configured to fix the correction lens thereto, a first holding frame configured to hold the fixing frame for movement in a first direction different from the direction of the optical axis of the lens groups, a second holding frame secured to the lens barrel and configured to hold the first holding frame for movement in a second direction different from the direction of the optical axis and the first direction, first and second driving sections including first and second coils and first and second magnetic field generation members opposing to the first and second coils and configured to move the first and second holding frames in the first and second directions, respectively, and first and second position detection sections configured to detect the amounts of movement of the fixing frame and the first holding frame in the first and second directions, respectively. At least one of the first and second magnetic field generation members and the first and second position detection means is provided on a fixed member secured to the lens barrel and including the second holding frame.
According to the anti-vibration apparatus disclosed in Patent Document 1 which has such a configuration as described above, an advantage can be anticipated that the anti-vibration apparatus can respond to vibrations of high frequencies without the increase of the cost and without the necessity for a large space.
Another existing lens apparatus is disclosed, for example, in Japanese Patent Laid-Open No. Hei 3-188430 (hereinafter referred to as Patent Document 2). In particular, Patent Document 2 discloses an image blur suppression apparatus for a camera for use for suppression of vibrations of the camera to which vibrations of comparative low frequencies are applied. The image blur suppression apparatus disclosed in Patent Document 2 is hereinafter referred to as second background art apparatus. The second background art apparatus determines, based on detection information of vibrations produced on a lens barrel, a correction amount for displacement of an optical axis necessary for suppression of image blur on an image plane and controlling the movement of a correction optical system, which is supported in a floating fashion so as to be movable in a diametrical direction with respect to the lens barrel, in accordance with the correction amount. The second background art apparatus includes a first holding frame configured to support the correction optical system in a floating fashion so as to support the correction optical system for movement in a first direction defined in a plane perpendicular to the optical axis but against movement in any other direction, and a second holding frame configured to support the first holding frame for movement in a second direction different from the first direction within the plane but against movement in any other direction. The second holding frame is secured to the lens barrel.
According to the anti-vibration apparatus for a camera disclosed in Patent Document 2 which has such a configuration as described above, an advantage can be anticipated that a problem of an out-of-focus state upon suppression of image blur is eliminated because the correction optical mechanism for displacing the optical axis in order to suppress image blur can be supported against movement by a configuration which does not provide a component of movement in the direction of the optical axis to the correction lens.
A further existing lens apparatus is disclosed, for example, in Japanese Patent Laid-Open No. Hei 10-311995 (hereinafter referred to as Patent Document 3). In particular, Patent Document 3 discloses a lens driving apparatus for an optical apparatus which is hereinafter referred to as third background art apparatus. The third background art apparatus is a lens driving apparatus which includes a first driving section configured to drive a lens accommodating section in which a lens is held in a first direction within a plane perpendicular to the optical axis of the lens, and a second driving section configured to drive the lens accommodating section in a second direction perpendicular to the first direction within the plane. The first and second driving sections are disposed along an axis parallel to the optical axis of the lens.
According to the lens driving apparatus disclosed in Patent Document 3 which has such a configuration as described above, an advantage can be anticipated that reduction in size of the lens driving apparatus for driving a correction lens for correcting blur of an image can be achieved (refer to paragraph [0039] of the Patent Document 3).
However, in all of the first to third background art apparatus, in order to detect the position of the correction lens, a position detection section formed from a combination of a light emitting element such as a light emitting diode and a light receiving element such as a semiconductor detection element is provided. Uneconomically, a great number of parts are demanded for the position detection section and also an increased number of assembly steps are requisite, which gives rise to a problem of increase of the cost.